Silent solar power
Solar panels are used on sailing boats so that noisy generators are not required. Solar power generates electricity silently without disturbing the quiet serenity of sail power, the only sounds are the wind in the sails and the bow cutting through the blue water.
Tough, waterproof and corrosion resistant solar panels
The solar power used on sailing boats need not be different to land-use solar panels in their function but all electrical components need to be waterproof. The solar panel frames and mountings must be corrosion resistant to prevent attack from the highly corrosive sea spray. If mounted on decks they need to be tough enough to withstand being stood on.
Components of a marine solar system
There are solar regulators designed specifically for marine use, for example those used on solar powered marine buoys, it does not need not be any different to the usual types available if it is installed under cover with the battery, but must be waterproof if it is going to be mounted outside with the solar panels.
There are no batteries designed specifically for marine use but deep cycle batteries are recommended for daily power storage and use. The term "deep cycle " means they can routinely be drained to low levels of charge, usually about 30% state of charge (SOG) without any detrimental effect to the battery cells. Deep cycle batteries are recommended whenever power is stored and used on a daily basis as they will last longer than normal vehicle starting batteries, although it is best to use sealed batteries such as absorbed glass matt (AGM ) or GEL batteries to avoid acid spillage in rough weather.
Wiring should be marine grade cable with UV resistant insulation. It must be capable of handling the charge current without any significant voltage loss. Cable used for low voltage use is thicker than high voltage wiring because it must carry a higher current flow for an equivalent power supply. The wiring should be rated to carry the measured solar amperage plus 50% to avoid power loss. For instance, a 140 watt solar panel generates about 8 amps and requires cable rated to carry 12 amps.
Where to mount solar panels on a boat
Because a boat is always moving there is no point in angling the solar cells toward the sun as one would for a land-based solar array. They are always mounted horizontally so that regardless of the boat's position it will get some sunlight. Unfortunately this also means less solar power is generated, so it may only generate about half the rated maximum power, in other words our 140 watt solar panel will only provide about 70 watts per hour of sunlight.
Blocking diode
A blocking diode is required if the solar panels are covered when not in use for an extended period of time, as this will prevent reverse current flow draining the battery if it remains connected to the solar panels. An alternative is to disconnect the battery.
If these facts are taken into consideration then 12 volt solar panels are a good option for sailing boat power. Happy sailing!
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